beagled/Lucene.Net/Search/Weight.cs

   1 /*
   2  * Copyright 2004 The Apache Software Foundation
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  * http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 using System;
  18 using IndexReader = Lucene.Net.Index.IndexReader;
  19
  20 namespace Lucene.Net.Search
  21 {
  22
  23         /// <summary>Expert: Calculate query weights and build query scorers.
  24         /// <p>
  25         /// The purpose of Weight is to make it so that searching does not modify
  26         /// a Query, so that a Query instance can be reused. <br>
  27         /// Searcher dependent state of the query should reside in the Weight. <br>
  28         /// IndexReader dependent state should reside in the Scorer.
  29         /// <p>
  30         /// A <code>Weight</code> is used in the following way:
  31         /// <ol>
  32         /// <li>A <code>Weight</code> is constructed by a top-level query,
  33         /// given a <code>Searcher</code> ({@link Query#CreateWeight(Searcher)}).
  34         /// <li>The {@link #SumOfSquaredWeights()} method is called
  35         /// on the <code>Weight</code> to compute
  36         /// the query normalization factor {@link Similarity#QueryNorm(float)}
  37         /// of the query clauses contained in the query.
  38         /// <li>The query normalization factor is passed to {@link #Normalize(float)}.
  39         /// At this point the weighting is complete.
  40         /// <li>A <code>Scorer</code> is constructed by {@link #Scorer(IndexReader)}.
  41         /// </ol>
  42         /// </summary>
  43         public interface Weight
  44         {
  45                 /// <summary>The query that this concerns. </summary>
  46                 Query GetQuery();
  47
  48                 /// <summary>The weight for this query. </summary>
  49                 float GetValue();
  50
  51                 /// <summary>The sum of squared weights of contained query clauses. </summary>
  52                 float SumOfSquaredWeights();
  53
  54                 /// <summary>Assigns the query normalization factor to this. </summary>
  55                 void  Normalize(float norm);
  56
  57                 /// <summary>Constructs a scorer for this. </summary>
  58                 Scorer Scorer(IndexReader reader);
  59
  60                 /// <summary>An explanation of the score computation for the named document. </summary>
  61                 Explanation Explain(IndexReader reader, int doc);
  62         }
  63 }